A generator system for a gas turbine engine, such as that found in aircraft, ships, and some terrestrial vehicles, may include three separate brushless generators, namely, a permanent magnet generator (PMG), an exciter, and a main generator. The PMG includes permanent magnets on its rotor. When the PMG rotates, AC currents are induced in stator windings of the PMG. These AC currents are typically fed to a regulator or a generator control device, which in turn outputs a DC current. This DC current next is provided to stator windings of the exciter. As the rotor of the exciter rotates, three phases of AC current are typically induced in the rotor windings. Rectifier circuits that rotate with the rotor of the exciter rectify this three-phase AC current, and the resulting DC currents are provided to the rotor windings of the main generator. Finally, as the rotor of the main generator rotates, three phases of AC current are typically induced in its stator, and this three-phase AC output can then be provided to a load such as, for example, an aircraft, ship, or vehicle electrical system.
Because some aircraft generators are high speed generators with potential rotational speeds up to and in excess of 24,000 rpm, various mechanical components may be supplied with lubricant. Moreover, some of the electrical components within the generator may generate heat due to electrical losses, and may thus be supplied with a cooling medium. These potentially high rotational speeds can also impose large centrifugal forces on various rotating components, such as the rotor. Given these potentially stressful operating conditions, cooling, rotor dynamics, material stresses, and bearing life may present certain design constraints that may adversely affect generator performance and manufacturing cost.
Hence, there is a need for a high speed generator that addresses the above-noted potential concerns. Namely, a high speed generator that supplies sufficient cooling to its mechanical and electrical components and/or improves rotor dynamics and/or reduces material stresses and/or provides increased bearing life. The present invention addresses one or more of these needs.